Large eddy simulation on influence of swirler structure on ignition performance
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摘要:
为研究旋流器结构对航空发动机燃烧室点火性能的影响，使用大涡模拟方法结合wall-adapting local eddy-viscosity（WALE）亚格子模型、动态增厚火焰模型，并设置单个脉冲火花，模拟了轴径向和双轴向旋流器燃烧室的点火过程。结果表明：相同结构和工况下，点火位置的流场因湍流脉动随时间变化，因而点火时刻会影响点火模拟结果。对于实验中能成功点火的结构和工况，为避免模拟时使用单脉冲火花影响点火结果，应选择在速度方向指向回流区，速度幅值小于平均值的时刻点火。对比轴径向和双轴向旋流器燃烧室的动态流场演变过程，发现双轴向旋流器燃烧室的火花正对旋转射流，点火位置瞬时速度指向回流区的概率更低，火焰更易向下游移动而非进入回流区。因此其点火性能劣于轴径向旋流器燃烧室。
Abstract:To investigate the influences of swirler structures on the ignition performance of aero-engine combustors, the large eddy simulation combined with the wall-adapting local eddy-viscosity （WALE） sub-grid model, the dynamic thickened flame model, and a single spark was used to simulate the ignition processes of an axial-radial swirler combustor and a dual-axial swirler combustor. Results indicated that the flow fields at the ignition position changed over time due to the turbulent fluctuation under the same structures and conditions, so the ignition time affected the simulation result. To avoid the use of a single spark in simulations against the ignition results on the condition that the combustor can be ignited successfully in experiments, the spark should be started when the instantaneous velocity pointed to the recirculation zone and the velocity magnitude was smaller than the average value. Comparing the dynamic evolution process of the flow field of the axial-radial swirler combustor with the dual-radial swirler combustor, it was found that the ignition position of the dual-axial swirler combustor was directly opposite to the swirler jet, and the probability of the velocity pointing towards the recirculation zone was lower. The flame was prone to propagate downstream rather than to the recirculation zone. Therefore, the ignition performance of the double-axial swirler combustor was worse than the axial-radial swirler combustor.
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Key words:
- ignition performance /
- lean ignition limit /
- combustor /
- large eddy simulation /
- swirler /
- fuel air ratio /
- flame propagation
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图 8 轴径向旋流器燃烧室50 ms时的点火过程
Figure 8. Ignition process in axial-radial swirler combustor at 50 ms
图 9 轴径向旋流器燃烧室在97.5 ms时的点火过程
Figure 9. Ignition process in axial-radial swirler combustor at 97.5 ms
图 12 两种结构中间截面旋涡中心的分布
Figure 12. Eddy distribution of two structures on the middle section
图 13 双轴向旋流器燃烧室点火位置径向速度变化
Figure 13. Variation of the radial velocity at ignition position of dual-axial swirler combustor
图 15 双轴向旋流器燃烧室燃油流量2.4 g/s时点火过程
Figure 15. Ignition process in dual-radial swirler combustor when fuel mass flow rate is 2.4 g/s
图 16 双轴向旋流器燃烧室燃油流量4 g/s时点火过程
Figure 16. Ignition process in dual-radial swirler combustor when fuel mass flow rate is 4 g/s
表 1 算例信息
Table 1. Information of calculation examples
算例 旋流器结构 燃油流量/（g/s） 点火时刻/ms 结果 1 轴径向 2.4 50.0 失败 2 轴径向 2.4 97.5 成功 3 双轴向 2.4 52.5 失败 4 双轴向 4.0 50.0 成功 
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